Hydraulic lash adjuster



Feb. 5, 1946. H. F. BARR HYDRAULIC LASH ADJUSTER Filed March 10, 1943Patented Feb. 5, 1946 2,394,354 HYDRAULIC LASH ADJUSTER Harry F. Barr,Detroit, Mich., assignor to General Motors Corporation, Detroit, Mich.,a corporation of Delaware Application March 10, 1943, Serial No. 478,6712 Claims. (Cl. 123-90) This invention relates to internal combustionengines and has particular reference to a hydraulic means to adjust theplay or lash in the valve mechanism.

The novelty of the structure relates to specific details ofconstruction; in the application of oil pressure below a plunger of thetappet construction; and enabling a constant and very gradual escape ofoil from under the plunger to relieve the pressure when excessivepressures tend to exist because of (1) the expansion of the parts due toheat, or (2) the upward movement of the tappet to unseat the usualpoppet valve. The plunger of the tappet is preferably provided with aninclined non-metallic washer, preferably made of a substance knowncommercially as neoprene. The purpose of the inclined washer is toenable a seepage of oil in one direction, but to prevent the passage ofoil in a reverse direction because the pressure of the oil will forcethe washer against the interior of the tappet cylinder.

n the drawing:

Figure 1 is a sectional view through a multicylinder internal combustionengine showing the application of the invention.

Figure 2 is an enlarged detailed sectional view of the structure of theinvention shown in Figure 1.

Figure 3 is a sectional view similar to Figure 2 of a modification.

Figure 4 is a detailed perspective view of the spacer ShOWn in Figure 3.

Figure 5 is a detailed perspective view of the retainer of Figure 3.

Referring to the drawing, the numeral 2 indicates an internal combustionengine as a whole. The engine has the usual cylinder block provided witha plurality of cylinders 4 in which operate the usual pistons 6connected in the usual way by means of a connecting rod (not shown) tothe usual crankshaft (not shown). The cylinder block has the usual waterpassages 8, and on top thereof there is the usual cylinder head It]bolted to the cylinder block in the usual Way. A gasket I2 isinterpositioned between the cylinder block and the head I0. The head H]has the usual water passages l4 and the usual combustion chamber l6. Oneof the poppet valves is shown at I8 and the bearing part 28 of the valveoperates in a bearing seat 22 formed in the head. The valve stem has theretainer 24 secured on the end thereof and a compressed coil spring 26is positioned between the retainer and a shoulder in the cylinder head.

The rocker arm shaft is indicated at 28 and on the shaft there aremounted a plurality of eccentric bearings 38 on each of which there ismounted a rocker arm 32. One end 34 of the rocker arm bears on the endof the stem of the valve 18 to operate it, and the other arm 36 hasmounted therein a ball shaped terminal 38 which rests on a correspondingseat 48 secured to the end of a push rod 42. The lower end of the pushrod is formed into ball shape as indicated at 44 and the ball 44 restsin a seat 46 formed in the end of a plunger 48 of the novel tappetconstruction indicated as a whole at 58. The tappet construction 58includes the tappet body 52 which has a flat lower surface 54 in contactwith the camshaft 56 and is operated by the cam 58. The tappet body 52is slidably mounted in a bearing seat 68 formed in the engine block.

A removable cover plate 62 is provided over an opening 64 in the side ofthe engine block and a gasket 66 is interpositioned between the cover 62and the edge of the opening 64. vThe opening 64 is to enable access tothe tappets 50.

Referring to Figure 2, it will be seen that the plunger 48 slidablyoperates in the tappet body 52.

The tappet body is cylindrical and has the exterior annular recess 68which is adapted to receive oil pressure from an oil line 18. Theplunger 48 has a reduced upper end 12 and the top of the tappet body 52is provided with an interior collar 14 held in place by a cotter pin 16.The collar 14 forms an abutment for the shoulder 18 of the plunger andlimits the upward movement of the plunger.

The plunger is provided with an annular recess 88 which is much longerthan the recess 68 but more or less parallels this recess 68. The recessextends well toward the bottom of the plunger so that the lower portionof the plunger is formed in a flange-like structure 82. This flange isun-'- dercut to give an inclined surface 84 and against the inclinedsurface there is received a correspondingly shaped washer 86 which has asharpened lower outer periphery 88 which presses against the innercylindrical wall of the bore of the tappet body 52. This washer 86 maybe made of any desirable material, but in the present invention ispreferably made from a plasticsubstance known commercially as neoprene.Below the washer 86 there is positioned the retainer 98,

the upper part of which is shaped to conform to the shape of the flange82 and the washer 86, but has a rounded periphery as indicated at 92,spaced from the wall of the tappet body 52.

The plunger 48 has a projection or extension 94 at its lower end, andover this projection or extension there are received the washer 88 andthe retainer 90.

The retainer has a recess on its underside and in the recess there isreceived the upper end of a coil spring 38 which is under compressionand which rests at its lower end in a seat 98 in the bottom of thehollow tappet body 52. The spring surrounds a cylindrical block I00, thelower end of which is positioned in a recess I02 formed in the bottom ofthe tappet body. The block I00 limits the lower movement of the'plungerand diminishes the size of the oil chamber II4 below the plunger. Thecoil spring 86 constantly urges the retainer 90 and the washer 86 upwardor against the plunger 48.

The wall of the tappet body has an opening I 04 which connects therecess 68 of the tappet body with the recess 80 of the plunger in orderthat oil pressure coming from the line I0 may pass into the-recess80.

The plunger 48 has a bore I06 and a lateral passage I08 connecting thebore I06 to the outside. In the bore I06 there is positioned a pin IIOto restrict the opening. The borel05 serves as an oil escape passage,and the size of the pin I I0 will determine the cross sectional area ofthe passage available as an escape opening.

The operation of the device is as follows: It is to be assumed that theentire space comprising the recesses 68 and 80 and the chamber H4 isalready filled with oil. The oil pressure'from the line I0 will passthrough the opening I04 and into the recess 80, and owing to theinclined position of'the washer 86 and the clearance space II2 betweenthe flange 82 and the inner wall of the tappet body 52, the oil underpressure will force its way through the space H2 and between the edge ofthe washer 06 and the tappet body into the space II4 below the plungerand below the retainer 90. When the cam strikes the fiat 54 on the endof the tappet body 52, the tappet body will be raised which will raisethe plunger 48 because the chamber I I4 is filled with oil underpressure. The oil pressure in the chamber II4 will constantly urge theplunger 48 upwardly which will prevent any play or lash at the joints.

When the valve tappet body 52 is lifted by the cam 58, the pressureexerted on the oil in the space II4 will increase. and in order to allowfor a metered escape of oil under conditions of high pressure, the boreI06 is provided. With this high oil pressure in the space II4, the oilwill be forced up the passage I06 and out of the passage I08 at acontrolled rate. thus compensating for the expansion of the valve trainparts caused by changes in temperature. Should the pressure tioned inthe bottom of the tappet body 52, is positioned at the top between theend of the tappet body 52' and a shoulder I I6 on the end of the plunger48'. The neoprene washer 86' is shaped differently in that the sharpedge 88 is not used. The retainer 30 also has a different shape and isbest shown in detail in Figure 5, and between the retainer 90' and thewasher 88' a spacer H8 is positioned. This spacer is shown in detail inFigure 4.

In the species of Figure 3 there is no extension 94 on the end of theplunger, and the pin 0' is rigidly secured in the bore I08 and extendsbelow retainer 90'. The dome I22 and shoulder I24 are provided with aplurality of small grooves I32 which serve as passages for the oil fromthe chamber 4' under the piston. The oilfrom the grooves I22 passes intoan annular groove I34 formed in the pin 0' and from the groove I34 theoil passes into the spiral groove I36 to the top I of the pin from whereit leaves the plunger and bore I 06 through the passage I08.

The spacer II8 has the collar I31, the top of which projects a l ttlebeyond the top of the dome I22 in the assembly shown in Figure 3.

The retainer has the lower inclined surface I38 which is adapted to seaton a correspondingly inclined surface I40 formed in the bottom of thetappet body 52'. The surfaces I38 and I40 serve as a limit stop for thedownward movement of the plunger 48.

The operation of the device is essentially the 40 same as that describedin connection with the in the chamber I I4 be reduced below the value ofthe pressure at the oil line I0, such as when the cam 58 leaves thesurface 54 of the tappet body, the pressure of the oil in therecess 80will cause the oil to be forced past the washer and into the space II4below the plunger 48, filling said space and thus compensating for thecontraction of the valve train parts caused by changes in temperature orthe loss of oil from space II4 during the valve lift event noted above.The block I00 has the advantage of forming a limiting stop for the lowermovement of the plunger and decreasing the oil volume in the space 4which increases In Figure 3 similar parts are designated by the samenumeral, or where there is a slight difference in the construction, aprimed numeral has been used. The spring 96', instead of beingposispecies of Figure 2. The oil enters the recess 68 and passes intothe recess through the opening I04. The oil will then seep past theclearance I I2 and between the edge of the Washer 86' and that wall ofthe tappet body 52', into the chamber I I4" below the plunger and theretainer. Due to high oil pressures during the valve lift interval, theoil will be forced through the grooves I32 into the recess I I 4' to theoutside of the plunger through the spiral passage I36, the bore I06, andthe passage I08. The oil pressure being constantly applied from the lineI0 will feed oil asis necessary into the chamber I I4 and the quantityof the oil in the chamber will be determined by the position of theplunger as varied by the degree of expansion and contraction of theparts. When the cam 58 forces the tappet body upward, the pressure inthe chamber 4' increases, and this increased pressure will force oilthrough the grooves I32 to the outside of the tappet body and plungerallowing a. slight contraction of the overall length of the tappetassembly during this cycle. Should the position of the parts be suchthat additional oil is needed in the chamber I I4, when the valve isagain seated the pressure from the line 10 will force the necessaryquantity of all past the neoprene washer 86'.

When high pressures are present in the chambers H4, 4'; the oil cannotbe forced in the reverse direction because the pressure against thewasher will force it more tightly against the inner walls of the tappetbody to prevent oil passing from the chambers H4 or H4 to the recess 80.

I claim:

1. In a hydraulic lash adjuster for the poppet valves of an internalcombustion engine, a hollow tappet body adapted to be actuated by thecamshaft of the engine, a plunger reciprocably mounted in said body andinterconnected with one of the valves to operate the same, said plungerhaving an annular recess, a resilient washer in the body below theplunger and seated thereagainst, said washer forming an oil'seal betweenthe plunger and the inner wall of the body, a retainer in the bodyseated under the washer, means on the end of the plunger to mount thewasher and the retainer, means to enable oil to exert pressure in therecess, the plunger and the washer enabling oil to pass from the recessto underneath the plunger to cause oil pressure to be exerted underneaththe plunger. a washer between the retainer and the seal, a plurality ofgrooves in the retainer to allow the passage of oil, and means in thplunger to receive oil from the said grooves and to enable the gradualescape of oil from underneath the plunger when high oil pressures existbelow the plunger.

2. In a hydraulic lash adjuster for the poppet valves of an internalcombustion engine, a hollow tappet body adapted to be actuated by thecamshaft of the engine, a plunger reciprocably mounted in said body andinterconnected with the valve to operate the same, said plunger havingan annular recess, a resilient washer in the body below the plungerandseated thereagainst, said washer forming an oil seal between theplunger and the inner wall of the body, a retainer in the body seatedunder the washer, means on the end of the plunger to mount the washe andthe retainer, means to enable oil to exert pressure in the recess, theplunger and the washer enablin oil to pass from the recess to underneaththe plunger to cause oil pressure to be exerted underneath the plunger,a washer between the retainer and the seal, a plurality of grooves inthe retainer to allow the passage of oil, a bore in the plunger, a rodin said bore, and a passage in the rod to receive oil from the saidgrooves and to enable the gradual high oil pressures exist below theplunger.

HARRY F. BARR.

